America's number one. One year -- today live so many people change forever as they lined streets of Boston. To watch the marathon and today -- will mark the anniversary of the bombing that killed three people and injured more than 260. Others and it started with -- scene yesterday when three. 3000 people showed up for. Photo shoot at the finish line to show their support ABC's -- rather live in Boston. With more good morning -- Good morning from Boston -- and that it was exactly one year ago that terrorists struck here. But it did not break the city's spirit the people here united. And they're going to stand united again today. Today a celebration Boston's resilience. The city pays tribute to the victims and survivors at the marathon bombings one year ago today. Two explosions at the finish line cut spending terror attack three people were killed. More than 260. Injured. Including resents it -- who lost a leg it is now learning to use a prosthetic. I don't think anybody knows what they're capable of doing insulin you're forced to ambient it's the same story for Heather -- another survivor. I learned that much -- More resilient than I ever could have imagined. Under enormous security survivors first responders and dignitaries -- walk to the finish line for a moment of silence at 2:49 PM. The exact time the first bomb went off. It's a very difficult day for families and survivors clearly one year anniversary of loss of a loved one. Change of -- life forever. But it's also I feel a big -- -- -- -- process. People around the country are also paying tribute. These runners race and a month long relay from Los Angeles to Boston to raise money for the wounded the runners traveled ten to twenty miles. Then passed the baton -- runners in another city. It's really cool to actually handle. Them you know that the time that it was handled from California to here so far. -- for the Boston Marathon now 118. Years old they'll run it next Monday with a new rally cry. We run together last year to -- Be the final word needs needs two. Go out and in really celebrated. Running as a great lifetime's board so that's that's why I'm going back. Back here live on a windy morning in Boston. Vice President Biden will join the governor of Massachusetts -- the mayor of Boston for this afternoon's tribute they're gonna raise a flag at the finish line. And church bells will ring out across the city. Diana and John credit he's -- rather live press in Boston this morning thank you. -- tune into ABC later today for live coverage of the anniversary including the moment of silence our coverage begins on the air and online at 2:35 eastern 11:35. Pacific.

This transcript has been automatically generated and may not be 100% accurate.

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